Quick answer: concentration equals milligrams of peptide divided by milliliters of solvent added. A 10 mg vial reconstituted with 2 mL gives 5 mg/mL, which is 5,000 mcg/mL, or 50 mcg per unit on a standard 100-unit (1 mL) syringe.
The three numbers that matter
- Peptide mass in the vial, printed on the label in mg.
- Solvent volume added, in mL. This is your choice and it sets the concentration.
- Syringe scale, the number of units on the syringe and the volume it holds.
The math
Divide mass by volume for mg/mL. Multiply by 1,000 for mcg/mL. Divide by the number of units per mL on the syringe for mcg per unit. To find the draw for a target amount, divide the target (mcg) by mcg per unit. Our peptide calculator does this and shows the draw as a red line on the syringe.
Worked example
10 mg vial, 2 mL bacteriostatic water, 100-unit syringe. 10 divided by 2 is 5 mg/mL, or 5,000 mcg/mL. 5,000 divided by 100 units is 50 mcg per unit. A 250 mcg target is 5 units.
Choosing a solvent
Bacteriostatic water is standard for research stocks because the preservative limits microbial growth in a multi-draw vial. Sterile water has no preservative and suits single-use preparations. Some hydrophobic peptides dissolve better with a small amount of dilute acetic acid; the paper you are following will say.
Technique
- Bring the vial to room temperature before opening.
- Run the solvent down the inside wall. Do not squirt it onto the powder.
- Swirl or tilt. Never shake; shear damages peptides and causes foam.
- Wait for a clear solution. Particles or cloudiness mean incomplete dissolution or degradation.
Record keeping
Log the batch number, the date, the solvent and volume, the resulting concentration, and the aliquot count. That is the line in your notebook that makes the experiment repeatable.
All Browse Peptides products are supplied for laboratory research use only and are not for human or veterinary use. This article summarizes published literature for research reference and is not medical advice, a protocol, or a recommendation of any kind.